Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$59.94	3.456%	$62.0115	$62.01	$62.00	$62.00
Purchase #2	$24.72	13.321%	$28.013	$28.01	$28.00	$28.00
Purchase #3	$220.56	5.133%	$231.8813	$231.88	$231.90	$231.90
Purchase #4	$100.76	3.665%	$104.4529	$104.45	$104.45	$104.50
Purchase #5	$222.82	13.114%	$252.0406	$252.04	$252.05	$252.00
Purchase #6	$30.34	5.259%	$31.9356	$31.94	$31.95	$31.90
Purchase #7	$121.48	4.575%	$127.0377	$127.04	$127.05	$127.00
7 purchase totals =	$780.62		$837.3726	$837.37	$837.40	$837.30